<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>

        .container{
            width:500px;
            height:300px;
            display:flex;
            justify-content:center;
            align-items: center;
        }

        .loading{
            font-size:35px;
        }

        .loading::after {
            content: '';
            animation: dot 2s infinite;
        }

        @keyframes dot {
            0% {
                content: '...'
            }
            25% {
                content: ''
            }
            50% {
                content: '.'
            }
            75% {
                content: '..'
            }
            100% {
                content: '...'
            }
        }
    </style>
</head>
<body>
<div class = "container">
    <span class="loading">加载中</span>
</div>
</body>
</html>
